In addition to offering technological advantages, femtocell deployments allow for precise fine-grained localization of mobile devices. With femtocell aided localization, as each femtocell base station's coverage area is small, it becomes possible to determine whether a device is inside a house, at a particular restaurant, near a specific park attraction, in a particular section of a store, or in a particular part of an office building. Femtocell-aided localization may become the preferred method of localizing devices in indoor environments given the challenge of using GPS receivers indoors. Additionally, femtocell-based localization may be preferable over localization based on IEEE 802.11 Wi-Fi hotspots since, while Wi-Fi is often turned off when not in use, cellular devices typically remain connected with the network at all times to be able to receive voice calls. Precise localization of mobile devices offers many exciting opportunities, for example in entertainment theme parks, where users will not only be able to determine their location on a map, but will also be able to interact with entertainment attractions (for example, play scavenger hunt games, unlock treasures, et cetera).
Third-party localization systems (TLSs) that map wireless station locations and use the information later to provide devices with estimates of their positions are becoming more and more common. TLSs are able to localize mobile devices due to wireless stations broadcasting their unique and persistent station identifiers.